Spark-plug.



Papduunem 1917. l

G. l;`.` HERZ.

SPARK PLUG.

APPucmon mio mi. al. un.` f

I citizen of the United States,

GUsTavE L. franz, oENEw Yoan, N. Y.

SPARK-PLUG.

To all whom it may concern.'

Be 1t known that I, GUsTAvn L. HERZ, a and resident of the boron h of Manhattan, in the city and useful Im rovement in Spark-Plugs,

State of ew Yorlnhave invented a new'and 0f which the ollowing is a specification.

In spark plugs heretofore produced where the insulator was cast `into the shell, it has beenfound practically impossible to ma1ntain a gas-tight connection between the in-A sulator and shell owin to the unequal eX- pansion of the materia s under the extreme variations olfheat to which the plugs are exposed.

i h e object of my` invention is to provide' certain improvements lug whereby the insulator is not only interin this type of spark ocked-to the shell but: is alsoV caused to have a' gas-tight connection therewith, under all heat. conditions. This object is obtained by providing the bore of the shell with one or more tapered ortions in which the insulator is forced tightly under all conditions of is app temperature,by the pressure of the gases in the engine cylinder t0 which the spark plug ied. In the present instance, I have shown the shell bore as having two tapered portions at different distances from the longitudinal 'axis of the spark plug, connected ya flaring portion. l 1 y A practical embodiment of my invention is represented in the accompanying'draw in which, s igure 1 represents my improved spark plzg in top plan,

, 1g. 2 1s a longitudinal central section through the same, and4 A Fig. 3l isv a `longitudinal central section through the shell. y

he spark plug comprises the shell l, the insulator 2and the central electrode 3.' The insulator 2 is composed of any suitable insulating material and. is .cast into the'shell inthe manufacture of the spark plug. The shell bore has, beginning at respectively., a cylindrical portion. 4, a tared portion 5, aiaring portion 6, anda 'second tapered portion?, interlocked at the two tapered portions whereby Sure.

its lnner end,l

under pressure.

outer end of theshell. The tapered portion 5 1s shown as nearer to the longitudmal axis of. the plug than the tapered portion 7. It 4 will be seen that when pressure 1s applied to the insulator, it will tend to force the insulator outwardly, giving it a wedginc' action in the tapered portions 5 and 7 of the shell, thus insuring a gas-tight connection ,between the insulator und shell at these points, irrespective of the relative different expansions of the material of the insulator and.shell. At the saine time the insulator is interlocked to the shell.

It is evident that the form shown is only one of many different embodiments of my invention and hence I do not wi'sh to limit myself to the particular embodiment herein shown and described, but

What I claim is:

1. A spark plug comprising a shell and an insulator cast therein, the'shell bore having the insulator has a gas-tight connection therewith because of its wedging action in tions, under pressure.

2. A spark plug comprising a shell and an insulator cast therein, the shell bore having two tapered portions connected by a iiaring portion whereby the insulator is interlocked to the shell and has a gas-tight connection therewith because of its wedging action in the tapered portions, under pressure'.

3. A spark plug comprising a shell and an insulator cast therein, the two tapered portions at different distances from the longitudinal axis4 of the plug, whereby the insulator has a gas-tight connection therewith because o action in the tapered portions, `under pres- 4. AV spark plug comprising a shell and an insulator cast therein, the shell bore having two ta ered portions at 'diierent distances lts wedging action in he tapered portions,

the tapered por- I shell; bore having its 'wedging fa. l f '1,229,74af

5. A spark plng'coniprisinvg a shell and 'an insulator cust therein, the shell bore having;`

, successively, n cylindrical portion, Ntapered portom a flaring portiomnnda second ta- 5 `pere d portion,w whereby the' 'insulator is lnteiflocked to the'shell und has a.' gus-tight 'connection therewith because` of its wedgmg fiction in thetupei'ed portions, under PII-@ In testimony, that I claim the foregoing 10 as myinvention, I have signed my numethis f 25th day of' Januaryl 1917. f

GUSTAVE 

